CN113390819B - A terahertz sensor - Google Patents

Abstract

The invention relates to a terahertz sensor which comprises a cover layer and a substrate. The cover layer is arranged opposite to the substrate, a metal microstructure array is arranged on one surface, opposite to the substrate, of the cover layer, a metal reflecting mirror surface is arranged on one surface, opposite to the cover layer, of the substrate, and a gap is formed between the metal microstructure array and the metal reflecting mirror surface. A gap between the cover layer and the metal reflector surface forms a microfluidic channel, the microfluidic channel is used for accommodating a liquid sample to be detected, and the height of the microfluidic channel is micron-sized. The invention takes the metal microstructure array as the metamaterial, the metal microstructure array, the metal reflecting mirror surface and the gap between the metal microstructure array and the metal reflecting mirror surface form the metamaterial wave absorber, and further, the quantitative and qualitative detection effect on the liquid sample is realized by utilizing the characteristics that the metamaterial is very sensitive to the change of the dielectric property of the surrounding environment, the resonance of a local electromagnetic field is obviously enhanced by the Fabry-Perot resonant cavity of the metamaterial wave absorber, and the unique properties of low photon energy, strong penetrability, fingerprint spectrum characteristic and the like of terahertz wave.

Description

A terahertz sensor

technical field

The invention relates to the technical field of liquid detection, in particular to a dual-band terahertz sensor integrated with a microfluidic channel in a metamaterial wave absorber.

Background technique

Terahertz waves refer to electromagnetic waves with a frequency in the range of 0.1 to 10 THz. It has broad application prospects in the field of biomedicine due to its unique properties such as low photon energy, strong penetration, and fingerprint characteristics. At the same time, as a label-free sensor, the terahertz sensor has broad application prospects in the field of biological trace detection. However, when most terahertz sensors detect liquid samples at present, the samples are dried and attached to the surface, which is too different from the solution environment of biomolecules, resulting in inaccurate detection results.

Contents of the invention

The purpose of the present invention is to provide a terahertz sensor to realize the quantitative and qualitative detection of liquid samples with accurate detection results and high precision.

To achieve the above object, the present invention provides the following scheme:

A kind of terahertz sensor, described sensor comprises cover layer and substrate;

The cover layer is arranged opposite to the substrate; the surface of the cover layer opposite to the substrate is provided with a metal microstructure array; the surface of the substrate opposite to the cover layer is provided with a metal mirror surface ; There is a gap between the metal microstructure array and the metal mirror surface;

The gap between the cover layer and the metal reflective mirror forms a microfluidic channel; the microfluidic channel is used to accommodate the liquid sample to be detected; the height of the microfluidic channel is in micron order.

Optionally, the metal microstructure array includes a plurality of resonant units uniformly arranged in rows and columns in two-dimensional space; the distance between two adjacent resonant units is 120-125 μm.

Optionally, the resonant unit includes a metal ring and a cross-shaped metal; each end of the cross-shaped metal is vertically provided with a strip of metal, and there is a gap between any two strips of metal; the cross-shaped metal Both the metal and the strip metal are located in the metal ring; the resonance unit is an axisymmetric structure.

Optionally, the strip metal is straight or curved.

Optionally, the microfluidic channel has a height of 4-6 μm and a width of 1000-5000 μm.

Optionally, the thickness of the cover layer is 40-100 μm; the material of the cover layer is silicon, quartz, polyimide, fluorine-containing polyimide, polyethylene or polytetrafluoroethylene.

Optionally, the thickness of the substrate is 10-500 μm; the material of the substrate is silicon, quartz or semiconductor material.

Optionally, the thickness of the metal microstructure array is 120-200 nm; the material of the metal microstructure array is Al, Au, Ag, Cu or Ti/Pt/Au.

Optionally, the thickness of the metal mirror surface is 120-200 nm; the material of the metal mirror surface is Al, Au, Ag, Cu or Ti/Pt/Au.

Optionally, the thickness and material of the metal microstructure array and the metal mirror surface are the same.

According to the specific embodiments provided by the invention, the invention discloses the following technical effects:

A terahertz sensor provided by the present invention includes a cover layer and a substrate. The cover layer is arranged opposite to the substrate, the side of the cover layer opposite to the substrate is provided with a metal microstructure array, the side of the substrate opposite to the cover layer is provided with a metal reflective mirror, and there is a gap between the metal microstructure array and the metal reflective mirror. void. The gap between the cover layer and the metal reflective mirror forms a microfluidic channel, which is used to accommodate the liquid sample to be detected, and the height of the microfluidic channel is in the order of microns. In the present invention, the metal microstructure array is used as the metamaterial, and the metamaterial wave absorber is composed of the metal microstructure array, the metal mirror surface and the gap between the two, and then the metamaterial is very sensitive to changes in the dielectric properties of the surrounding environment, The Fabry-Perot resonant cavity of the metamaterial wave absorber can significantly enhance the resonance of the local electromagnetic field, and the unique properties of the terahertz wave, such as low photon energy, strong penetration, and fingerprint characteristics, realize the detection of liquid samples. Quantitative and qualitative detection function. Use microfluidic channels to control the liquid sample to be detected at the micron level to reduce the strong absorption of water on terahertz, and generate two resonance peaks with high absorption rate and high Q value in the 0.2-1.4THz frequency band, which significantly improves the detection sensitivity . At the same time, the metal microstructure array is set in the microfluidic channel, and the microfluidic channel is located in the medium layer of the metamaterial wave absorber, so as to realize the rapid and convenient detection of trace liquid samples. The overlapping of the reflection cavity of the material wave absorber enhances the local electromagnetic field, improves the detection sensitivity, the detection result is accurate, and the detection accuracy is high.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of a sensor provided by Embodiment 1 of the present invention.

FIG. 2 is a schematic structural diagram of the metal microstructure array provided by Embodiment 1 of the present invention.

FIG. 3 is a schematic structural diagram of a resonance unit provided by Embodiment 1 of the present invention.

FIG. 4 is an absorption spectrum diagram of the sensor provided in Example 1 of the present invention under samples with different refractive indices.

FIG. 5 is a graph showing the results of the frequency offset of the sensor as a function of the refractive index provided by Embodiment 1 of the present invention.

Fig. 6 is an x-z electric field distribution diagram at the resonant frequency point of the sensor provided by Embodiment 1 of the present invention.

Symbol Description:

1-cover layer; 2-substrate; 3-metal microstructure array; 4-metal mirror surface; 31-resonant unit; 311-metal ring; 312-cross metal; 313-strip metal.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The purpose of the present invention is to provide a terahertz sensor to realize the quantitative and qualitative detection of liquid samples with accurate detection results and high precision.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

This embodiment is used to provide a terahertz sensor. As shown in FIG. 1 , the sensor includes a cover layer 1 and a substrate 2 .

The cover layer 1 is arranged opposite to the substrate 2 . A metal microstructure array 3 is provided on the side of the cover layer 1 opposite to the substrate 2, and a metal mirror surface 4 is provided on the side of the substrate 2 opposite to the cover layer 1, that is, the metal microstructure array 3 is attached to the cover layer 1 and faces the substrate. On one side of the bottom 2 , a metal mirror surface 4 is attached to the side of the substrate 2 facing the cover layer 1 , and there is a gap between the metal microstructure array 3 and the metal mirror surface 4 . Through this structural setting, the metal microstructure array 3 is used as the metamaterial. Metamaterial is a kind of artificial composite electromagnetic material. The special electromagnetic characteristics can be customized on demand by adjusting the resonant unit of the metamaterial. It is very sensitive to changes in the environment and can be applied in the field of sensing. And the metamaterial wave absorber is composed of the metal microstructure array 3, the metal mirror surface 4, and the gap between the metal microstructure array 3 and the metal mirror surface 4. As one of the typical structures of metamaterials, the metamaterial wave absorber is mainly composed of Composed of metal-dielectric-metal three-layer structure, the Fabry-Pérot cavity of the metamaterial absorber can significantly enhance the resonance of the local electromagnetic field, and has the characteristics of high absorption rate, lightness and thinness.

The gap between the cover layer 1 and the metal mirror surface 4 forms a microfluidic channel, which is used to accommodate the liquid sample to be detected, and the height of the microfluidic channel is on the order of microns. By setting the microfluidic channel between the cover layer 1 and the metal mirror surface 4, that is, the lower surface of the cover layer 1 is used as the upper surface of the microfluidic channel, and the upper surface of the metal reflective mirror surface 4 is used as the lower surface of the microfluidic channel. The metal microstructure array 3 is located in the microfluidic channel, and the microfluidic channel is located in the medium layer of the metamaterial wave absorber, which realizes the fast and convenient detection of trace liquid samples. When the terahertz wave passes through the microfluidic channel, due to the The liquid sample to be detected in the microfluidic channel coincides with the reflective cavity of the metamaterial wave absorber, which can enhance the local electromagnetic field and improve the detection sensitivity of the sensor. At the same time, there is still the problem of strong absorption of water to terahertz waves in liquid detection, which makes less terahertz waves carry information about the sample, which also leads to inaccurate detection results. In this embodiment, by setting the height of the microfluidic channel It is at the micron level, and the microfluidic channel can be used to control the liquid sample at the micron level to reduce the strong absorption of water on the terahertz, and generate two resonances with high absorption rate (99.9%) and high Q in the 0.2-1.4THz frequency band Peak, significantly improve the detection sensitivity of the sensor, the sensitivity can reach 300GHz/RIU.

Specifically, when the sensor of this embodiment is used to detect a liquid sample, when the terahertz wave is incident perpendicular to the surface of the sensor, it passes through the cover layer 1, the metal microstructure array 3, and the microfluidic channel, and then is reflected back by the metal mirror surface 4, and then Quantitative and qualitative detection of liquid samples to be tested. In this embodiment, the thickness of the metal mirror surface 4 is greater than the skin depth of the terahertz wave in metal, so no transmission will occur.

Microfluidic technology has gradually been applied in the field of sensing because it can detect liquids at the micron or nanoscale level. Among them, the terahertz sensor designed by combining microfluidics with metamaterial wave absorbers has become a new trend in the field of terahertz sensing. big research hotspot. The sensor provided in this embodiment mainly utilizes that the metamaterial is very sensitive to the change of the dielectric properties of the surrounding environment, and the Fabry-Pérot cavity (Fabry–Pérot cavity) of the metamaterial absorber makes the local electromagnetic field resonate significantly Enhanced characteristics, as well as unique properties such as low photon energy, strong penetration, and fingerprint characteristics of terahertz waves, realize qualitative and quantitative detection of trace liquid samples. At the same time, the microfluidic channel is placed in the medium layer of the metamaterial wave absorber, and the liquid sample to be detected is located in the microfluidic channel, which highly overlaps with the reflective cavity of the metamaterial wave absorber, which can enhance the local electromagnetic field and improve the sensor performance. Sensitivity, and set the height of the microfluidic channel to the micron level, reduce the strong absorption of water on terahertz, and further improve the sensitivity of the sensor. That is to say, the sensor provided in this embodiment combines the metamaterial wave absorber with the microfluidic channel, controls the liquid sample to be detected at the micron level, and at the same time enhances the local electric field, realizing high-sensitivity detection of trace liquids, and accurate detection results ,High precision. The sensor has potential applications in non-destructive fast and label-free detection.

As an optional implementation, as shown in FIG. 2 , the metal microstructure array 3 includes a plurality of resonant units 31 uniformly arranged in rows and columns in a two-dimensional space, and the distance between two adjacent resonant units 31 is It is 120-125 μm, and there is a gap between two adjacent resonance units 31 . When calculating the distance between two adjacent resonant units 31, since the structures of the resonant units 31 are exactly the same, the distance between the center points of the adjacent two resonant units 31 can be directly used as the distance between the adjacent two resonant units 31. spacing between.

Further, as shown in FIG. 3 , the resonance unit 31 includes a metal ring 311 and a cross-shaped metal 312 . Each end of the cross-shaped metal 312 is vertically provided with a metal strip 313 , there is a space between any two strips of metal 313 , and both the cross-shaped metal 312 and the strip of metal 313 are located in the metal ring 311 . The resonant unit 31 is an axisymmetric structure, and the specific symmetry axes are the two sides of the cross-shaped metal 312. The resonant unit 31 may also be a rotationally symmetric structure, which can be overlapped by rotating 45 degrees. It can be considered that the cross-shaped metal 312 and strip-shaped metal 313 in this embodiment form a double H-shaped cross structure, and this embodiment uses the metal ring 311 and the double H-shaped cross structure as the resonant unit 31, which can further Improve sensor performance.

More specifically, the strip metal 313 is straight or curved. As shown in Figure 3 (a), it provides a structural schematic diagram of the resonant unit 31 when the strip metal 313 is linear, and as shown in Figure 3 (b), it provides a schematic diagram of the resonance unit 31 when the strip metal 313 is curved. The structural schematic diagram of the resonant unit 31. However, no matter which structure of the resonant unit 31 is used, the sensor of this embodiment can produce two absorption rates as high as 99.9% in the range of 0.2-1.4THz while using the microfluidic channel to reduce the strong absorption of water for terahertz waves. The resonant peak, the Q value can reach 40, and the sensitivity can reach 300GHz/RIU, which significantly improves the detection sensitivity of the sensor, and the detection result is accurate and the precision is high.

As an optional embodiment, the height of the microfluidic channel is 4-6 μm, and the width is 1000-5000 μm. When the structural parameters of the microfluidic channel are set within the above range, the detection sensitivity of the sensor can be further improved.

The thickness of the cover layer 1 is 40-100 μm, and the material of the cover layer 1 is silicon, quartz, polyimide, fluorine-containing polyimide, polyethylene or polytetrafluoroethylene. The thickness of the substrate 2 is 10-500 μm, and the material of the substrate 2 is silicon, quartz or semiconductor material. The thickness of the metal microstructure array 3 is 120-200 nm, and the material of the metal microstructure array 3 is Al, Au, Ag, Cu or Ti/Pt/Au. The thickness of the metal mirror surface 4 is 120-200nm, and the material of the metal mirror surface 4 is Al, Au, Ag, Cu or Ti/Pt/Au. Preferably, the metal microstructure array 3 and the metal mirror surface 4 are made of metal aluminum with an electrical conductivity of 3.56×10 ⁷ S/m. More preferably, the metal microstructure array 3 and the metal mirror surface 4 have the same thickness and the same material. When the actual structural parameters of the sensor are within the above range, the detection sensitivity and detection accuracy of the sensor can be further improved.

This embodiment also verifies the detection performance of the above sensors. Specifically, the resonance unit 31 shown in FIG. 3(a) is applied to sensor A, and the resonance unit 31 shown in FIG. 3(b) is applied to sensor B. The simulation software CST verifies the dual-band terahertz sensor integrated with the microfluidic channel of the two metamaterial absorbers shown in Figure 3. When verifying, the specific structural parameters of the sensor used are respectively: the structural parameters shown in Figure 1 are: the length of the cover layer 1, the metal mirror surface 4 and the substrate 2 are the same, the length P=125 μm, and the thickness tc of the cover layer 1 = 50 μm, the thickness t of the metal microstructure array 3 = 0.2 μm, and the height h of the microfluidic channel = 5 μm. The structural parameters of the resonance unit 31 of the sensor A shown in Fig. 3 (a) are: the outer diameter r=53 μm of the metal ring 311, the length lx=39 μm of the strip metal 313, the side length ly=58 μm of the cross-shaped metal 312, and the width w = 5 μm. The structural parameter of the resonant unit 31 of sensor B shown in Fig. 3 (b) is: outer diameter r1=57 μ m of metal ring 311, strip metal 313 is the arc section taking the center of cross-shaped metal 312 as the center of a circle, and its outer diameter r2 = 37 μm, the distance g between two adjacent metal strips 313 = 15 μm, and the width w = 6 μm.

Fig. 4(a) schematically shows the absorption spectra of sensor A under samples with different refractive indices, and Fig. 4(b) schematically shows the absorption spectra of sensor B under samples with different refractive indices. It can be seen that when there is no sample in the microfluidic channel, both sensors produce two resonance peaks with an absorption rate as high as 99.9% in the 0.2-1.4 THz frequency band. When the refractive index of the liquid sample to be detected changes from 1 to 2, the resonant peaks of both sensors show obvious frequency shift. This shows that these two sensors can convert the small refractive index change of the liquid sample into an obvious frequency shift phenomenon, and the sample detection can be realized only by detecting the change of the frequency shift. Here, Q=f ₀ /FWHM is defined, where f ₀ is the resonant frequency, FWHM is the full width at half maximum of the resonant peak, and Q represents the resonant property of the sensor. Sensor A produces resonant peaks at 0.64THz and 0.88THz. Through calculation, it can be known that the Q values of sensor A at the low frequency and high frequency resonant peaks are 32 and 44, respectively. Sensor B produces resonance peaks at 0.6THz and 0.86THz. Through calculation, it can be known that the Q values of sensor B at low frequency and high frequency resonance peaks are 30 and 43, respectively. That is to say, it is proved again that the two sensors of this embodiment can generate two resonance peaks with high absorption rate and high Q value in the range of 0.2-1.4 THz while using the microfluidic channel to reduce the strong absorption of water for terahertz waves. The detection sensitivity of the sensor can be significantly improved.

Figure 5(a) schematically shows the results of the shift of the resonant frequency of sensor A as a function of the refractive index of the sample, and Figure 5(b) schematically shows the shift of the resonant frequency of sensor B as a function of the refractive index of the sample The result graph of the rate change. It can be seen from Figure 5 that the frequency shift of the two sensors maintains a linear relationship with the refractive index of the sample. Here, the refractive index sensitivity S=Δf/Δn is defined, Δf is the frequency shift, Δn is the variation of the refractive index, and the sensitivity S is the slope of the linear fitting curve shown in FIG. 5 . After calculation, the sensitivities of sensor A at the low-frequency and high-frequency resonances are 206GHz/RIU and 300GHz/RIU respectively, and the sensitivities of sensor B at low-frequency and high-frequency resonances are 193GHz/RIU and 295GHz/RIU respectively. exhibited high sensitivity. At the same time, define FOM=S/FWHM to characterize the overall performance of the sensor. It can be calculated that the FOM values of sensor A at low frequency and high frequency resonance are 10.3 and 15 respectively, and the FOM values of sensor B at low frequency and high frequency resonance are 9.7 and 14.8 respectively. Compared with the existing sensors, the overall performance of the two sensors described in this embodiment is improved, and the two resonance peaks reflect more sample information, which improves the detection accuracy. The microfluidic channel is located in the medium layer of the metamaterial wave absorber, and the liquid sample to be detected in it is highly coincident with the reflective cavity of the metamaterial wave absorber, so that the local electromagnetic field is enhanced, thereby improving the sensitivity of the sensor. The metal mirror makes the terahertz wave localized on the metal surface without transmission phenomenon, thereby increasing the number of times the terahertz wave passes through the sample, making the reflected terahertz wave carry more sample information and improving the detection accuracy.

Figure 6(a) schematically shows the x-z electric field distribution diagram of sensor A at its low-frequency resonance frequency point, and Figure 6(b) schematically shows the x-z electric field of sensor A at its high-frequency resonance frequency point Distribution diagram, Figure 6(c) schematically shows the x-z electric field distribution diagram of sensor B at its low-frequency resonance frequency point, and Figure 6(d) schematically shows the sensor B at its high-frequency resonance frequency point The x-z electric field distribution map. It can be seen from Figure 6 that the incident electromagnetic wave energy is mostly concentrated in the microfluidic channel and the cover layer 1, and the liquid sample to be detected is located in the microfluidic channel to enhance its interaction with the local electromagnetic field, which effectively improves the sensitivity of the sensor and realizes the solution Sample testing.

This embodiment is aimed at sensing and detecting trace liquid samples in biomedicine. The liquid sample is injected into the microfluidic channel, which acts as a dielectric layer, and the metal microstructure and the metal mirror 4 form a metamaterial absorber, forming a strong resonance structure, thereby realizing high-Q and high-sensitivity sensing and detection.

In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the present invention Thoughts, there will be changes in specific implementation methods and application ranges. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (7)

1. A terahertz sensor, characterized in that the sensor comprises a cover layer and a substrate;

the cover layer is arranged opposite to the substrate; a metal microstructure array is arranged on one surface, opposite to the substrate, of the cover layer; a metal reflecting mirror surface is arranged on one surface of the substrate, which is opposite to the cover layer; a gap is formed between the metal microstructure array and the metal reflector surface;

a gap between the cover layer and the metal reflector forms a microfluidic channel, and the metal microstructure array is positioned in the microfluidic channel; the microfluidic channel is used for accommodating a liquid sample to be detected; the height of the microfluidic channel is micron-sized; the height of the microfluidic channel is 4-6 μm, and the width of the microfluidic channel is 1000-5000 μm;

the metal microstructure array comprises a plurality of resonance units which are uniformly arranged in a two-dimensional space in a row-column mode; the distance between two adjacent resonance units is 120-125 μm; the resonance unit comprises a circular metal ring and cross-shaped metal; strip-shaped metals are vertically arranged at each end part of the cross-shaped metal, and a gap is formed between any two strip-shaped metals; the cross-shaped metal and the strip-shaped metal are both positioned in the circular metal ring; the strip metal is in a curve shape;

the thickness of the cover layer is 40-100 μm; the thickness of the substrate is 10-500 μm; the thickness of the metal microstructure array is 120-200nm; the thickness of the metal reflecting mirror surface is 120-200nm and is larger than the skin depth of terahertz waves in metal.

2. The sensor of claim 1, wherein the resonating element is an axisymmetric structure.

3. The sensor of claim 1, wherein the material of the cover layer is silicon, quartz, polyimide, fluorine-containing polyimide, polyethylene, or polytetrafluoroethylene.

4. The sensor of claim 1, wherein the substrate is of a material that is silicon, quartz, or a semiconductor material.

5. The sensor of claim 1, wherein the metal microstructure array is made of Al, au, ag, cu, or Ti/Pt/Au.

6. The sensor of claim 1, wherein the material of the metallic mirror surface is Al, au, ag, cu or Ti/Pt/Au.

7. The sensor of claim 1, wherein the metal microstructure array and the metal mirror face are the same thickness and material.

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